제출 #255272

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
255272		Erkhemkhuu	통행료 (IOI18_highway)	C++17	0 / 100	35 ms	14584 KiB

highway

#include <bits/stdc++.h>
#include <highway.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define F first
#define S second
const int N = 100005;
pair <ll, ll> par[N];
vector <int> w;
vector <vector <pair <ll, ll> > > adj(N);
ll flat[N], timer;
void dfs(ll v, ll p) {
    flat[timer++] = v;
    for(auto &u: adj[v]) {
        if(u.F == p) continue;
        par[u.F] = {v, u.S};
        dfs(u.F, v);
    }
    return;
}
void find_pair(int n, vector <int> u, vector <int> v, int a, int b) {
    ll i, m, max_cost, l, r, mid, s, t;
    m = u.size();
    for(i = 0; i < m; i++) {
        adj[u[i]].pb({v[i], i});
        adj[v[i]].pb({u[i], i});
    }
    dfs(0, -1);
    w.resize(m, true);
    max_cost = ask(w);
    w.resize(m, false);
    l = 1; r = m;
    while(l + 1 < r) {
        mid = (l + r) / 2;
        for(i = l; i <= mid; i++)
            w[par[flat[i]].S] = true;
        if(ask(w) >= max_cost) {
            r = mid;
            for(i = l; i <= mid; i++)
                w[par[flat[i]].S] = false;
        }
        else l = mid;
    }
    s = flat[l];
    w.resize(m, false);
    dfs(s, -1);
    l = 1; r = m;
    while(l + 1 < r) {
        mid = (l + r) / 2;
        for(i = l; i <= mid; i++)
            w[par[flat[i]].S] = true;
        if(ask(w) >= max_cost) {
            r = mid;
            for(i = l; i <= mid; i++)
                w[par[flat[i]].S] = false;
        }
        else l = mid;
    }
    t = flat[l];
    answer(s, t);
    return;
}

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